Multiplex transmission of messages by high-frequency oscillations



Dec. 9, 1 24. 5 1,518,401

' 7 H. FASSBENDER ET AL MULTIPLEX TRANSMISSION OF MESSAGES BY HIGH FREQUENCY OSCILLATIONS Filed May 5, 1921- 1 2 Sheets-$heet 1 1 7 9.1; 2503571 5503'? 1 3805.7 (g A B: 0 I I 1'7; 1155mm I -1 777 700 l I f ZZZZ '-1 78000- m Dec. 9 1924- H. FASSBENDER ET AL LSISAUE MULTIPLEX TRANSMISSION OF MESSAGES BY HIGH FREQUENQK OSCILLATIONS Filed May 15, 1921 2 Sheets-Sheet 2 M: '//Wf W MW JZZL/VWM.

Patented Dec. 9, 1924.

UNITED STATES PATENT OFFECE.

HEINRICH FASSBENIDER, 0F CHARLOTTENBURG, AND ERIGH I-IABANN, OF BERLIN, GERMANY, ASSIGNORS TO DEUTSCHE TELEPHGNJTERKE, G. M. B. H., OF BERLIN,

GERMANY.

MUTLTIPLEX TRANSMISSION OF MESSAGES BY HIGI-LFREQUENCY OSCILLATIONS.

Application filed May 3, 1921.

To (ZZZ whom it may concern:

Be it known that we, HEINRICH FAssnnNnnn and Enron HABANN. both German citizens, and residing at Charlottenburg, Germany, and Berlin, Germany, have invented certain new and useful Improvements in Multiplex Transmission of Messages by High-Frequency Oscillations (for which we have filed applications in Germany, 4th September, 1918, 28th January, 1919, and 5th September, 1919; in Switzerland, 12th February, 1919; in Sweden, 3 0th March, 1920, and in Holland, 29th April, 1920), of which the following is a specification.

The subject of the invention is a conductor for multiplex high frequency telephony and telegraphy of which the chiciency is increased by suiting the high frequency oscillations, which are used simultaneously, to particular sections of the conductor in such a manner that the whole conductor can accommodate along its whole length between its end stations the longest wave'which can occur in working, on which wave the telegraphic or speaking currents can be superposed by known means, whilst to sections of the conductor are imparted correspondingly shorter high frequency basic oscillations for the simultaneous communication in other directions, according to the rule, that these basic oscillations (wave lengths) are in the same relation to each other as the squares of the conductor sections on which they are used. These waves also serve as carriers of the telegraphic signs or of speech.

The reception of the various messages at the end of the separate sections and at "the end of the whole conductor is ensured inf th'e'know'n man'nerby tuning the receiver.

The stations of the section are provided with tuned transmitting and receiving devices, which are simply connected to the section atany time, so that each tuned receiving device only receives from the conductor the particular wave intended therefor; butallows the remaining waves to" pass without obstruction A partial relative 5t! overlappingof the sections doesnot cause any difiiciilty' as; an interfii'iiighfig" of the waves does not occur,

Serial No. 486,524.

By using the conductor in sections for multiplex purposes and arranging the frequencies according to the lengths of these sections the damping factor for all sections becomes equal or substantially equal in a simple manner without the necessity of using for this purpose amplifying devices or similar equalizing devices, although these may be used if desired. This uniform or substantially uniform damping factor on all sections. c uses the clearness to be equally good on all the sections.

This is due to the following consideration. The degree of clearness depends upon the damping which the conductor possesses for the frequency used. If in fact only one frequency comes into question, the dimensions and electrical sizes of the conductor can easily be so chosen that the damping does not exceed a determined limit with a. given length of conductor. It is however different for multiplex telegraphy and telephony where a number of different frequencies are used at the same time on the conductor.

L (where K is the capacity of the conductor per centimeter, and L the self inductance of the conductor per centimeter) for every frequency 72 musthave a different value so as to give the same value ,6 for all conversations in the known formula for the damping exponents.

In this case the quotient Lzthe self induction per centimeter of the conductor. As for high frequencies the losses by leakance can be neglected the following formula will apply:

Further in conseque cc of the skin effect the following also applies:

wherein it, is a constant, 1' the radius of the conducting wire, a the frequency. From this follows The total damping for two conductor lengths Z Z wlth frequencies 9%,, a, 1s there fore - kl K (o aled 1,

The clearness over both conductor lengths an approximate result would suffice in practree.

The damping itself may be suitably chosen (within natural limits), as the formula as will be seen is independent of the magni tude of L and K, which determine the damping. There 15 therefore the possibility that the ratio L ample, that for the longest wave, therefore for the longest section, a particularly favorable value of the damping M is obtained.

K L ever be chosen in such a manner that it produces the same damping (@Z) already for must be so chosen, for etc- By approximation the quotient can howa somewhat smaller section according to the fOlHllllZl 5 above.

The practical application of the invention can be carried into efiect in two ways. Either the conductor sections of various lengths, as they are given by the main communicating centres (large towns, and so forth) are arranged in series, or the whole conductor is divided into a number of sections for the different frequencies so that it provided for the highest frequency (shortest wave length) with the greatest number of sections, whilst its whole length serves for the lowest frequency (longest wave).

In the drawing both ways are illustrated diagrammatically.

Figure 1 shows a whole section AE,

which is divided into subsections AB, B 'C, CD, D-E, by additional stations connected thereto. The stations A and E connnunicate with wave, whilst the end stations of the said subsections communicate with each other by shorter waves, which correspond to the square of the length of the section. For example the stations B and C communicate with each other by a longer wave than the stations A, B or C, D or D, E. Between C and D transmitted the shortest wave. A longer wave than between B and C however passes between the stations A and C, A and D, B and D, D and E. C can also communiate with E by a separate wave. In Figure l, for example, the distances between the stations are indicated in kilometers and the wave lengths, which are used on the separate sections according to the invention, are also indicated.

Figure 2 shows a conductor wherein the waves are arranged according to the second method of communicating sections. In this case the whole length of the conductor is divided into equal or substantially equal sections, and communication is efiected for example between stations E and A by first passing from A to B, then from B to C, from C to D, and finally from D to E, or vice versa, whereby the shortest wave length, which is made to suit these subsections, is used. At the same time, however, a message passes from B to H over the two equal sections B-Qll, EH, connected together, with a corresponding longer wave length. In this case devices must be provided for effecting the automatic transmission from one to the next equal section. Between unequal sections, which is the case entirely in Figure 1, such devices must effect simultaneously a transformation of the frequency. Such arrangements of both kinds can be constructed in the known manner. An undesired passage of the waves from one section to another is prevented by blocking devices also of known type.

each other by the longest.

In-FigureB,.forexainp'le, is illustrated the workingci-rcuit corresponding to- F igur'e-Z, wherein the station B transmits to E over the stationsC, D, the stationC being a transforming station and converts the frequency a, on the section- 133G to the lower freque'ncyn, required for thesecti'on (IE. At the-same time (or at" another time); the stationDtransmits over A. on the single section D-(J, alsokat afrequen'cy" 715, on the section C A i of double, the length" with a lower frequency 72. The station B is not formed as a transforming station, but', as illustrated in the figure, simply allows the frequency n topass. Also in the first mentioned communicationfrom B over C, D to E, the station D allows-the frequency to pass. Also anothercom-munication takes I placesimultaneously or at another time from stationB over C, D, E to the station I-I not shown, therefore over six single sections (see Fig. 2)" and. this in two equal jumpsB, E,:E H each of thefrequency a which is still lower than 01,. In this case the station E is a transforming station without changing the frequency, whilst the stations C, D, F, G simply allow the frequency a, to pass.

In Figure 4 is illustrated a transforming station C. As st-ated above it must transform the frequency n, to n, in bothdirections-whilst it simply allows the frequency in, to pass. For this purpose blocking systems Kn Kn, (each consisting of a condenser and acoil) are-provided at the station, which are loop-resonant to the frequencies m, n, and allow the frequency a to pass, but prevent the passage of the frequency n,, from left to right or from right to left, or the return to the right or left of the frequencies it, sent left or right respectively over the systems Kn, Kn, The frequency a, from the left is received on the correspondingly tuned oscillating circuit En of which the other accessory appliances (recti fiers, amplifiers) are not shown. The oscillating energy finally energizes a relay R, which consequently operates the transmitter S12 producing the frequency a, and transmitting it towards the right. In this manner the blocking point for communication between B to E with a change of frequency is bridged over. Similarly the frequency a, coming from the right is received on the right by the tuned receiving system En, and the energy energizes the telephone T which in its turn transmits the signs and speech to the micro hone M. The latter sets the transmitter n, to the left of the speaking position in operation, which transmits the frequency to the left from the station A.

In Figure 5 is illustrated the station E. This receives the frequency a, passing from the right of Figure 4 and serves as a transmitting station for the frequency 11 The systems lin Km are inserted for blocking both frequencies. The frequency it, (coming from the left) is received by the tuned receiving system. Em, and the energy, for

example, is conducted to an amplifying tube V behind which the actual receiver (telephone or telegraph apparatus) above the switch a is reached.

If the switch it were in another position the frequency a, would pass on unchanged but amplified as the energy directly energizes the transmitting system Sa which produces the frequencyn and transmits it to the right. Similarly the frequency 92 coming from the left is re so close togetherthat the conductor affords a good path for the shorter waves passing therethrough, but only so close together that" above all those waves, which pass through at least of the total length of the conductor, are transmitted favorably. The short waves on. the other hand are trans mitted well in spite of the insufficient dis tribution of the coils as they pass through correspondingly shorter sections. These short waves are on their part not influenced by those Pupin coils which are not adapted for their lengths as they pass around these coils by passing through the condensers.

If the conductor is composed of strands for avoiding skin effects, then according to the invention the division of the cross sec tion of the conductor by forming strands is only carried out so far that the ohmic resistance of the strand for all waves, which pass at least through ,4; of the length of the conductor, is practically the same as for continuous current. In this manner a practical and completely effective improvement is produced at a. low cost, as the strand contains a comparatively small number of wires.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is 2- 1. In multiplex transmission of messages by high frequency oscillations of different frequencies, a conductor divided into sections, and receiving and transmitting stations connected to the various sections, the frequencies of the waves passing through the conductor being disposed for the various sections in such a manner that the wave length used on a section and the wave length used on any one other section are proportionated to each other in the same ratio as the square of length of the former section and the square of the length of the latter section are proportionated to each other.

2. In multiplex transmission of messages by high frequency oscillations of different frequencies, a conductor divided into sections, and receiving and transmitting stations connected to the various sections, the frequencies of the waves passing through the conductor being disposed for the various sections in such a manner that the wave length used on a section and the wave length used on any one section are proportionated to each other in the same ratio as the square of length of the former section and the square of the length of the latter section are proport-ionated to each other, the conductor being formed of strands, the member of which is so chosen that the ohmic resistance of the conductor due to wave frequency is practically removed for the longest waves i. e. the waves used over a distance at least equal to of the total conductor-length.

3. In multiplex transmission of messages by high frequency oscillations of different frequencies, a conductor divided into sections, and receiving and transmitting stations connected to the various sections, the frequencies of the waves passing through the conductor being'disposed for the various sections in such a manner that the wave length used on a section and the wave length used on any one other section are proportionated to each other in the same ratio as the square of the length of the former section and the square of the length of the latter section are proportionated to each other, means connected to some of the sections for automatically transferring Waves of certain frequencies from one section to another and means for transforming the frequency of another part of the Waves as they pass from one section to another.

4%. In multiplex transmission of messages by high frequency oscillations of different frequencies, a conductor divided into sections, and receiving and transmitting stations connected to the various sections, the frequencies of the waves passing through the conductor being disposed for the various sections in such a manner that the wave length used on a section and the Wave length used on any one other section are proportionated to each other in the same ratio as the square of the length of the former section and the square of the length of the latter section are proportionated to each other, loop resonant circuits tuned to certain frequencies and inserted between adjacent sections to prevent the passage of these frequencies from section to section without passing through the station which lies between these two sections, the said station being adapted to receive in one case a. message in its recording apparatus and to let pass in anothercase the message, means being provided in the latter case for amplifying the energy of the by-passing wave and if needed for changing the frequency thereof.

HEINRICH FASSBENDER. ERIGH HABANN. 

